Riparian habitats provide organic matter inputs that influence stream biota and ecosystem processes in forested watersheds. Over a 13-yr period, we examined the effects of litter exclusion, small- and large-wood removal, and the addition of leaf species of varying detrital quality on organic matter standing crop and export of organic and inorganic particles in a high-gradient headwater stream. Using eight pretreatment years of export data and two pretreatment years of particulate organic matter (POM) standing crop data, we report on 21 and 15 years of continuous export and POM standing crop results, respectively. Litter exclusion resulted in the elimination of leaf standing crop by the end of year three. Wood and fine benthic organic matter (FBOM) standing crops declined significantly during the exclusion and wood removal periods, but never completely disappeared. Following the introduction of artificial wood structures for retention, the addition of fast, slow, and mixed breakdown leaves in the treatment stream resulted in significantly increased mean annual leaf standing crops. After five years of leaf addition, FBOM standing crop and fine particulate organic matter (FPOM) export remained below pre-treatment levels. The reduction in leaf standing crop in the treatment stream resulted in significant increases in FPOM (23), fine inorganic particulate (33), and gravel export (103). After small wood removal we observed significant increases in export of fine inorganic particulates (23) and gravel (73) from the treatment stream. A greater proportion of coarse and FBOM standing crop was exported from the treatment stream during the litter exclusion and small wood removal periods than from the reference stream. Following the addition of slow and mixed leaves this trend was reversed, demonstrating the importance of leaf standing crop in the retention of POM. Our long-term experiment demonstrates that the quantity and type of riparian inputs to forested headwater streams will affect POM standing crop and export of POM and sediments to downstream ecosystems, and that small wood is more critical to retaining sediments and POM in small streams than previously recognized.

dc.description.sponsorship

National Science Foundation DEB-9207498, DEB-9629268, DEB-0212315

dc.language.iso

en_US

dc.publisher

Ecological Society of America

dc.subject

allochthonous

dc.subject

appalachian (usa) streams

dc.subject

coweeta hydrologic laboratory,

dc.subject

north carolina, usa

dc.subject

detrital complexity

dc.subject

detritus

dc.subject

leaf litter

dc.subject

exclusion

dc.subject

organic matter standing crop

dc.subject

organic matter transport

dc.subject

sediment transport

dc.subject

seston

dc.subject

storms

dc.subject

wood

dc.subject

food-web

dc.subject

mountain stream

dc.subject

forest-stream

dc.subject

woody debris

dc.subject

terrestrial

dc.subject

dynamics

dc.subject

carbon

dc.subject

retention

dc.subject

litter

dc.subject

transport

dc.title

Storage and export of organic matter in a headwater stream: responses to long-term detrital manipulations